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Publication numberUS6051779 A
Publication typeGrant
Application numberUS 08/752,858
Publication dateApr 18, 2000
Filing dateNov 21, 1996
Priority dateNov 21, 1996
Fee statusPaid
Also published asCN1130962C, CN1238115A, DE69710604D1, EP0940068A1, EP0940068B1, WO1998023139A1
Publication number08752858, 752858, US 6051779 A, US 6051779A, US-A-6051779, US6051779 A, US6051779A
InventorsJohn Weldon Gammon
Original AssigneeEricsson Inc.
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Shield can with integrally molded gasket
US 6051779 A
Abstract
An improved RF shielding device is disclosed. An RF shielding device includes a shield can having sidewalls defining a number of guide tabs thereon enabling the shield can to be inserted within a molding apparatus such that an electrically conductive gasket may be molded directly to the sidewalls of the shield can.
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Claims(6)
What is claimed is:
1. A shield can for shielding components on a printed circuit board from electromagnetic interference, comprising:
a shield can plate having a peripheral edge thereon;
a sidewall extending from the shield can plate and having a first end connected to the peripheral edge of the shield can plate and a second end defining at least one tab integrally formed with the second end of the sidewall and extending parallel therefrom for aligning the shield can with a gasket mold, wherein the second end of the sidewall further has a known position variance with respect to the shield can plate; and
a gasket integrally fitted to an edge of the second end of the sidewall, wherein the gasket has a predefined shape with a width fixed at a substantially constant distance independent of variations in position of the second end of the sidewall, wherein the distance is approximately equal to the known position variance of the second end of the sidewall.
2. The apparatus of claim 1 wherein the gasket is composed of an electrically conductive material.
3. A shield can, comprising:
a shield can plate for protecting circuitry on a printed circuit board from RF energies;
a sidewall extending from the shield can plate having a first end connected to an edge of the shield can plate, wherein a second end of the sidewall has a known position variance with respect to the shield can plate; and
a gasket integrally fitted to an edge of the second end of the sidewall, the gasket providing a low conductive resistance interfaced with the printed circuit board, the gasket further has a predefined shape with a width fixed at a substantially constant distance independent of variations in position of the second end of the sidewall, wherein the distance is approximately equal to the known position variance of the second end of the sidewall.
4. The apparatus of claim 3 further including a plurality of tabs integrally formed with the second end of the sidewall.
5. The apparatus of claim 3 wherein the gasket is composed of an electrically conductive material.
6. A shield can, comprising:
a shield can plate for protecting circuitry from RF energies;
a sidewall extending from the shield can plate having a first end connected to an edge of the shield can plate;
a plurality of tabs integrally formed with a second end of the sidewall for aligning the sidewall with a gasket molding apparatus, wherein the second end of the sidewall has a known position variance with respect to the shield can plate; and
a gasket integrally fitted to an edge of the second end of the sidewall, the gasket providing a surface for engaging a printed circuit board, the gasket further has a predefined shape with a width fixed at a substantially constant distance independent of variations in position of the second end of the sidewall, wherein the distance is approximately equal to the known position variance of the second end of the sidewall.
Description
BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to RF shielding applications, and more particularly, to RF shield cans having over molded gaskets.

2. Description of Related Art

In electronic application such as cellular telephones, RFI/EMI shielding is necessary to protect and shield sensitive components from interference generated by other components and external sources. Important design considerations of RF shielding involve minimizing the required board area for the RF shield. This involves consideration of the RF shield footprint, placement accuracy of the RF shield and allowance for component clearances.

Previous methods of connecting RF Shields have included directly soldering the metal shield can to a printed circuit board. While soldering provides an excellent ground contact between the shield and the printed circuit board, this method produces a permanently attached shield can that cannot be readily removed if post-solder assembly or testing is required of the protected circuits. Another method of RF shielding involves the use of electrically conductive adhesive as a bond between the shield and the printed circuit board. However, this approach requires a larger footprint on the printed circuit board to allow an adequate surface area for the adhesive bond.

A final method of shield can connection utilizes a dispensed gasket applied to the edge of the RF shield. A dispensed gasket requires a considerably wider width than the can sidewall to allow for adequate bond surface and to compensate for variation in the position of the sidewall location. Current dispensing technology requires the gasket bead to overlap both sides of a thin sidewall to stabilize and harden properly. The gasket width must be further enlarged to accommodate sidewall positioning tolerances and dispensing process tolerances. This occupies a larger area on the printed circuit board, reducing the amount of available space for components.

SUMMARY OF THE INVENTION

The present invention overcomes the foregoing and other problems with an improved RF shielding apparatus. The apparatus consists of an RF shield can having a top surface and sidewalls extending from the peripheral edge of the top surface. The sidewalls define a number of guide tabs enabling the shield can to be aligned with a gasket molding apparatus into which the sidewalls of the shield can are inserted. Once the sidewalls of the shield can have been inserted into a molding apparatus a gasket molding procedure directly molds an electrically conductive gasket to the sidewalls of the shield can. The gasket has a fixed geometry (width and shape) that is not dependent on variations in positioning of the sidewall of the RF shield can.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the method and apparatus of the present invention may be obtained by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein:

FIG. 1 is an in view of a prior art embodiment of a dispensed gasket;

FIG. 2 is an exploded perspective view of an RF shield can with a gasket molding apparatus;

FIGS. 3a-3c illustrate end views of a gasket and sidewall; and

FIG. 4 is a perspective view of a shield can with a molded gasket thereon.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Referring now to the drawings, and more particularly to FIG. 1, wherein there is illustrated a prior art embodiment of a dispensed gasket 5 along the edge of a shield can sidewall 10. The dispensed gasket process, required the gasket 5 overlap both sides of the sidewall 10 to bond properly. The width of the gasket 5 must also insure that the overlap accounts for variations in the sidewall 10 position.

Referring now to FIG. 2 there is illustrated an RF shield can 15 and gasket molding apparatus 20. The RF shield can 15 includes a top surface 25 and sidewalls 30 extending downwardly therefrom. The downwardly extending sidewalls 30 define a number of alignment tabs 35 for properly aligning the shield can 15 with the gasket molding apparatus 20. While FIG. 2 has been illustrated showing the use of alignment tabs 35, it should be realized that the tabs are not necessary, and the shield can 15 may be aligned within the gasket molding apparatus 20 utilizing manual means, vision systems or any other means for properly aligning the shield can 15.

The shield can 15 is placed within the gasket molding apparatus 20 such that a gasket may be over molded along the edges of the sidewall 30. The molding process utilized may include a liquid injection molding, silicone rubber injection over molding or other suitable process. The over-molded gasket material will comprise any electrically conductive material sufficient for maintaining a low conductive resistance interface between the RF shield and the printed circuit board. By over molding the gasket directly to the sidewalls 30 of the shield can 15 using molding apparatus 20, the width of the gasket 40 is fixed at a substantially constant distance as shown generally in FIGS. 3a through 3c. Since the sidewalls 30 of the shield can 15 are aligned within the mold of the gasket molding apparatus 20, variances in the sidewall position are automatically accounted for within the gasket. As can be seen in FIGS. 3a through 3c, no matter where the sidewall 30 may be positioned, the sidewall will always rest within the width 45 of the molded gasket 40 because the gasket is molded directly to the edge of the sidewall within the gasket molding apparatus 20. This allows the width of the gasket 40 to be substantially reduced from those of prior art embodiments and reduce the printed circuit board area required for the shield can 15 and gasket 40.

FIG. 4 illustrates the shield can 15 with the over-molded gasket 40. As can be seen, the gasket 40 has a much higher placement accuracy in smaller geometry area than the dispensed gasket for the prior art illustrated in FIG. 1. Reduction of the gasket outline width reduces the area required for placement of the shield can 15 on the printed circuit board 50 and reduces the tolerances that must be maintained for adjacent components or RF shields.

Although a preferred embodiment of the method and apparatus of the present invention has been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it is understood that the invention is not limited to the embodiment disclosed, but is capable of numerous rearrangements, modifications, and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US4098633 *Jan 24, 1977Jul 4, 1978The United States Of America As Represented By The Secretary Of The NavyMethod of making radiation seal
US4575578 *Jan 5, 1983Mar 11, 1986Keene CorporationRadiation shielding and thermally conductive gasket with internal bonding agent
US5068493 *Oct 17, 1990Nov 26, 1991Vanguard Products CorporationDual elastomer gasket shield for electronic equipment
US5205751 *Feb 21, 1992Apr 27, 1993Motorola, Inc.Electrically-conductive elastomeric connector
US5633786 *Aug 21, 1995May 27, 1997MotorolaShield assembly and method of shielding suitable for use in a communication device
US5717577 *Oct 30, 1996Feb 10, 1998Ericsson, Inc.Gasketed shield can for shielding emissions of electromagnetic energy
EP0643551A1 *Sep 5, 1994Mar 15, 1995Parker-Hannifin CorporationForm-in-place EMI gaskets
Non-Patent Citations
Reference
1 *IBM Technical Disclosure Bulletin vol. 33, No. 6A, Nov. 1990 Casting Seals for Disk Files, XP000107757 pp. 366 367.
2IBM Technical Disclosure Bulletin vol. 33, No. 6A, Nov. 1990 Casting Seals for Disk Files, XP000107757 pp. 366-367.
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US6420649Aug 18, 1997Jul 16, 2002Helmut KahlProcess for shielding an electric or electronic circuit and shielding cap
US7005573Feb 12, 2004Feb 28, 2006Parker-Hannifin CorporationComposite EMI shield
US7087835Oct 19, 2004Aug 8, 2006Bi-Link Metal Specialties Inc.Apparatus and method for shielding printed circuit boards
US7280855Jun 28, 2005Oct 9, 2007Research In Motion LimitedMicrophone coupler for a communication device
US7326862Jan 26, 2004Feb 5, 2008Parker-Hannifin CorporationCombination metal and plastic EMI shield
US7518880Feb 6, 2007Apr 14, 2009Bi-LinkShielding arrangement for electronic device
US7535726Mar 8, 2006May 19, 2009Research In Motion LimitedSystem and method for assembling components in an electronic device
US7796398Mar 16, 2009Sep 14, 2010Research In Motion LimitedSystem of components in an electronic device
US7797025Jun 15, 2007Sep 14, 2010Research In Motion LimitedMicrophone coupler for a communication device
EP1455564A1 *Mar 5, 2003Sep 8, 2004Sony Ericsson Mobile Communications ABElectronic device provided with an EMI shield
EP1739933A1 *Jun 28, 2005Jan 3, 2007Research In Motion LimitedCommunication device with shielded microphone
Classifications
U.S. Classification174/384, 174/370
International ClassificationH05K9/00
Cooperative ClassificationH05K9/0015
European ClassificationH05K9/00B2
Legal Events
DateCodeEventDescription
Oct 18, 2011FPAYFee payment
Year of fee payment: 12
Oct 18, 2007FPAYFee payment
Year of fee payment: 8
Oct 20, 2003FPAYFee payment
Year of fee payment: 4
Nov 21, 1996ASAssignment
Owner name: ERICSSON, INC., NORTH CAROLINA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:GAMMON, JOHN WELDON;REEL/FRAME:008310/0511
Effective date: 19961115